SPE-LC-MS/MS optimisation using response surface methodology for quantification of pharmaceuticals, pesticides and organic UV filters included in water protection guidelines.

The environmental concern about micropollutants (MPs) in aquatic environments has grown significantly in recent decades due to their widespread occurrence and potential risks to ecosystems and human health. Monitoring of MPs is crucial for understanding the status of aquatics systems, supporting risk assessments, developing elimination strategies, and informing regulatory decision-makers. However, due to the very low concentrations of MPs (usually ranging between ng L-1 and μg L-1 levels), their quantification requires highly sensitive and precise analytical methods. Solid phase extraction (SPE) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) has emerged as the preferred technique for analysing MPs in water. Nonetheless, developing multi-residue analytical methods remains challenging due to the diverse nature of these compounds. Specifically, in SPE, various parameters can significantly influence the efficiency of the process and, therefore, optimisation strategies are needed to reduce time, costs and environmental impacts. This study focuses on using design of experiments (DoE) with response surface methodology (RSM) aiming to optimise, for the first time, an SPE-LC-MS/MS method for the analysis of pharmaceuticals, pesticides and organic UV filters included in the European Union (EU) water protection guidelines. The optimised SPE conditions (sample pH of 3-4, sample volume of 375 mL, and 3.5 mL of ethanol (EtOH) as the eluent) resulted in a MPs average extraction efficiency (EE) of 65 %, matrix effect (ME) of 8 %, and an absolute recovery (AR) of 73 %. Accordingly, the SPE-LC-MS/MS method was successfully validated for routinely monitoring 32 target MPs in surface water (SW) matrices.